Turf grass (sod) is a living organism that must be handled properly to ensure its survival when it is removed from one location and transplanted to another. Sod is generally harvested using large machinery that cuts slabs of sod from the soil and stacks them on pallets.
FIG. 1 illustrates a portion of a sod harvesting machine 100 that includes a typical cutting head, conveyor system, and stacking system. The cutting head of FIG. 1 includes a chop mechanism 110, an oscillating blade 103, and a roller 104. Chop mechanism 110 is configured to periodically descend into the sod 151 to make vertical cuts defining an initial width/length of the slabs. Oscillating blade 103 oscillates back and forth underneath the sod to sever the slab from the underlying soil 150. Roller 103 applies pressure to the sod as it is cut to facilitate the cutting of clean slabs. Slabs cut by the cutting head are routed to conveyor 101 which lifts the slabs up to stacking conveyor 102 from which they are removed by a stacking head 105 for stacking on a pallet. Typically, the pallet is positioned adjacent to the stacking conveyor so that the stacking head can move back and forth between the stacking conveyor and pallet when stacking.
It is generally desirable to harvest sod as quickly as possible. However, various factors limit the speed at which sod can be harvested primary of which is the rate at which sod can be stacked on a pallet. For example, the ground speed of the sod harvester directly defines the rate at which sod is harvested. However, even if a sod harvester is capable of cutting sod from the ground at a faster rate, the sod harvester may still be limited by the rate at which the sod can be removed from the stacking conveyor and stacked on the pallet. In other words, the ground speed of sod harvester 100 is limited by the rate at which the stacking head 105 can remove sod from stacking conveyor 102.
Even if a stacking head can be operated quickly to increase the rate of sod harvesting, the increased rate does not necessarily yield a net gain in efficiency. For example, operating the stacking head at high rates can require substantial additional amounts of energy leading to increased fuel costs. These increased fuel costs may offset any gains resulting from the increased rate of sod harvesting. Also, operating at high rates increases the forces on the components of the stacking head leading to more frequent and costly repairs and corresponding downtime. Accordingly, the stacking head oftentimes forms the bottleneck during the sod harvesting process.